The introduction of steam-launches and small
pleasure-boats driven by steam-power is of comparatively recent
date, but their use is rapidly increasing. Those first built
were heavy, slow, and complicated; but, profiting by experience,
light and graceful boats are now built, of remarkable swiftness,
and having such improved and simplified machinery that they require
little fuel and can be easily managed. Such boats have strong,
carefully-modeled hulls, light and strong boilers, capable of
making a large amount of dry steam with little fuel, and a light,
quick-running engine, working without shake or jar, and using
steam economically.

The sketch [to the right] represents the engine built by
a New York firm for such little craft. This is the smallest size
made for the market. It has a steam-cylinder3 inches in diameter
and a stroke of piston of 5 inches, driving a screw 26 inches
in diameter and of 3 feet pitch. The maximum power of the engine
is four or five times the nominal power. The boiler is of the
form shown in the illustrations of semi-portable engines, and
has a heating-surface, in this case, of 75 square feet. The boat
itself is like that seen [above], and is 25 feet long, of 5 feet
8 inches beam, and draws 2.5 feet of water. These little machines
weigh about 150 pounds per nominal horse-power, and the boilers
about 300...

Source: A History of the
Growth of the Steam-Engine, by Robert H. Thurston, A. M.,
C. E., Professor of Mechanical Engineering in the Stevens Institute
of Technology, Hoboken, N. J.; Member of the Institution of Engineers
and Shipbuilders of Scotland, Associate British Institution of
Naval Architects, etc., etc. Published; New York: D. Appleton
and Company, 549 and 551 Broadway. 1878.